Robert Buderi, The Invention that Changed the World: How a Small Group of Radar Pioneers Won the Second World War and Launched a Technological Revolution; New York: Simon & Schuster, 1996(excerpt from Chapter 13, "The New Astronomers," reproduced with the kind permission of the author)

The star of the show was an unassuming Tennessean with a longtime fascination with the moon. In 1922, as a sixteen-year-old ham radio operator, John H. DeWitt Jr. had built Nashville's first broadcasting station, a fifteen-watt outpost with the call letters WDAA. For nearly two decades he had worked in radio while cultivating a love of astronomy. In May 1940, DeWitt had attempted to detect radio signals reflected off the lunar surface by a self-made eighty-watt transmitter. The experiment failed because of power losses and lack of receiver sensitivity. Before he could try again, the war had intervened. DeWitt joined the Army, first as a civilian consultant, then as a uniformed Signal Corps major. By the end of the war, he was a lieutenant colonel and running the Evans Lab. The Army had given DeWitt a second excuse to find the moon. Immediately after V-J Day, worried that the Soviets had captured enough German rocketry expertise to build ballistic missiles capable of reaching the United States, the Pentagon directed the Evans group to study how such invadors could be detected and tracked. At that point, for all radar's effectiveness against German and Japanese aircraft, scientists were not convinced that radio waves could penetrate the ionosphere, bounce off a target, and be detected back on Earth. DeWitt seized the opportunity to settle the matter. With no space-going rockets in existence to test his radar systems, he recalled, "I thought, well, if we could hit the moon with radar, we could probably detect the rockets." Lieutenant Colonel DeWitt dubbed the unofficial study Project Diana, after the virgin Roman goddess of the moon and hunting. As the Evans director, DeWitt supervised seventy officers and 1100 civilians. At war's end, most had little to do. He selected diminutive, bespectacled E. King Stodola as chief scientist of a five-man team and got down to business. The main piece of equipment was n SCR-271 early warning radar operating on a wavelength of 2.6 meters. The set had been modified by Major Edwin H. Armstrong, an Army consultant during the war famous for pioneering frequency modulation, the FM type of transmission common in modern radios. The enemy capitulation had ended the major's Army work, but not before he had cobbled together jump wires and temporary connections to turn the once ordinary radar set into a powerful transmitter and sensitive receiver. DeWitt's group further modified the receiver by employing a tunable crystal that could pick up an elusive return signal whose frequency would be Doppler-shifted by the relative motions of the Earth and moon. Two conventional antennas were married into a forty-foot-square bedspring affair and mounted on a tower overlooking the ocean. The high-gain antenna could be steered in azimuth only, not elevation, and so could be used only for half-hour periods at moonrise and moonset, when its target rode near the horizon. On January 10, 1946, everything finally came together. Several minutes after the moon rose at 11:48 in the morning, the first radar pulses were beamed skyward. Rather than the microsecond bursts used in wartime tracking, the set belched out a quarter-second-long signal with a great clatter of the mechanical transmit-receive switch. To allow time for the moon's return echo to arrive, the transmitter waited in silence for 4.75 seconds before sending out another pulse. DeWitt had driven into the nearby town of Belmar for lunch and cigarettes, and missed the big event. Harold Webb and Herbert Kauffman were hunched inside the large control shack when the first faint lunar echo arrived just before noon. Besides viewing the signal on a cathode ray screen, the men listened over loudspeakers to the response - a half-second-long hum like the buzz of an untuned radio set. Although they couldn't be absolutely certain it was the moon answering their call, Webb and Kauffman grew excited. The historic signal had arrived about 2.4 seconds after a pulse had gone out, and at the speed of light that would be just about the right amount of time for a radio wave to journey 240,000 miles or so into space and back. Besides, it had to be the moon they detected, DeWitt later stated, "because there was nothing else there but the moon."